2009 Fat Bob - Spark Knock? - Harley Forum

Violated · #1 08-28-2009, 04:46 AM

First, I'd like to say thanks in advance to all the people here to help people like me with motorcycle problems. I've already had the chance to review some closely related issues however, the solutions provided have not worked (probably because the issue is not the same...).

I currently have 3100km on my bike, but the problem has persisted since approx 800km. I've taken it in to the dealer and couldn't re-create the knock while I was there. At my 1600km service, this issue was one of the things I asked them to keep an ear open for, however they were not able to detect that knock that I heard. After a lengthy ride this summer, at approx 2500km, I was able to bring the bike in again; This time, they were able to hear the issue I was concerned with. Their first impression was that it may be the compensator in the primary and when the opened it up, the only thing the could see was that the auto-tensioner was a little loose and helped it along. The bike was started and the problem sounded like it was gone...

...Unfortunately, about 10km later (on the ride home and as the bike warmed up) the knock came back. I immediately went back to the dealer and had them listen to it again. At this point, their answer to me was that they know this 'knock' is there and that it's well documented and that if it gets worse, I should return to them at that point.

Now, I was born at night, but not last night, so I did a little research on this and everything seems to point to a couple of possible issues.

1. Spark Knock - Could I be hearing a detenation issue here? If so, I'm sure waiting on this issue is just shortening the life of my engine.

2. Engine mount - Loose maybe (but I have checked all the bolts and they are tightened to spec.

3. ???

ANY and ALL suggestions / solutions / comments are welcomed, as I'm at a loss here and don't want my bike to suffer any preventable damage.

Thanks again.

EDIT: To amplify the 'knock' in question and to better give you an understanding of what I'm hearing is as follows: This knock doesn't stop; weather the bike is under load, at idle, 2 up, standing still, at varing speeds up to and including 100+km/hr. It sounds like someone knocking on a plank of wood. The rate of knock varies through RPM however, at idle, it sound approx. 3-4 per second. I hope this helps.

shovelmike · #2 08-28-2009, 08:49 AM

Welcome to the forum. That knock sounds more like a mechanical knocking as opposed to spark knock since load doesn't affect it. Back in the early/mid 70's while auto makers were struggling to meet EPA specs with carbureted, non-catalyst equipped cars carbon build up in the combustion chamber was very common and it would sound just like a bad wrist pin or broken piston as it rattled around in there, it had some very experienced mechanics pulling heads expecting the worst. I have not heard of this issue with Harleys but it's one of those off the wall things you encounter from time to time.
Perhaps some other ideas will get thrown out here, in the meantime the dealer has left you with just one choice, ride it like you stole it so if it blows up it will be on Harley's tab.

Gas Man · #3 08-28-2009, 10:19 AM

Its for sure coming from the motor or primary?

Not a loose tank mount?

Violated · #4 08-28-2009, 03:18 PM

When listening to it using a spike to the boltheads, the sound seems like it's coming from the primary, but as I said, they took it apart and found nothing. This leads me to believe that it could be anything.

I'll have a look at the tank mounts in the meantime.

Hammerhead Pat · #5 08-28-2009, 03:26 PM

Make sure to keep everything documented!!!!!

street bob · #6 08-28-2009, 06:03 PM

I also had a sound that you are describing, only when it was at running temp. It turned out to be a bad connecting rod!!!

Violated · #7 09-03-2009, 03:59 AM

Street bob, this may be it then cause the sound is not there at a cold start. Only when the bike is warm.

I'll check it out.

Not to be oblivious, but what's a 'connecting rod'?

evoKENevo · #8 09-03-2009, 06:53 AM

A connecting rod is the arm that connects your crank shaft to a piston...subject to bearing failure among other things...but not neccesarily the source of your "knocking" noise.

In any case...this definately sounds like a warranty issue...and if I were you I'd drop the bike off at the dealer and tell them I'll be back when it's fixed...noting that it sounds to me like they just can't be bothered with diagnosing a problem that may eventually show itself if/when the engine blows...possibley at speeds that could KILL you if it seizes up, for example.

Violated · #9 09-05-2009, 02:00 AM

Thanks Ken,

After posting my last one, I looked it up as well.

So...Took the bike back to the dealer today, and the person I talked to said he couldn't hear the knock that I was talking about (even with me there present and pointing it out to him). They once again took apart my primary and re-adjusted my compensator, even after I suggested that this may be a connecting rod issue.

...And of course, this issue is still there. Just wasted my time there is all.

Anyone know of a GOOD ind mech certified by HD that can do warranty work in Victoria, BC Canada? Or at least someone in the area who could listen to this issue so I may get a second opinion?

Thanks.

tommyglide · #10 09-05-2009, 03:41 AM

Hey violated, HD of Prince George is a very good performance shop and its a very nice ride to get there.